The researchers looked for patterns in the states with the highest corruption rankings, and determined that money was a key connecting factor. Whether bribery, big-ticket spending for political favors or even pay raises for lawmakers, money seemed to flow more freely in states where corruption was more widespread.

The words "Tennessee" and "corruption" in the same sentence will likely remind readers of a certain age of the Rocky Top federal investigation of the 1980s, and the Tennessee Waltz probe in 2005.

In Rocky Top, FBI investigators learned that fake charities were chartered to obtain bingo licenses. Those organizations then set up bingo operations that funneled part of their earnings back to the state lawmakers who cooperated with them. More than 50 people were convicted, and several prominent state legislators were taken down, including then-House Majority Leader Tommy Burnett.

The Tennessee Waltz investigation ultimately nabbed seven state legislators for accepting bribes in exchange for sponsoring and supporting legislation. Local leaders, including two county commissioners, were also arrested for their roles in the scheme.

In 1979, before those two highly-publicized investigations, Tennessee Governor Ray Blanton's administration was shaken by a cash-for-clemency scandal. Two of Blanton's top aides and a state trooper were convicted. Blanton was never charged in connection with that affair, but he was convicted on separate charges of mail fraud, conspiracy and extortion. He served nearly two years in federal prison.